configfs: new object reprsenting tree fragments

Refcounted, hangs of configfs_dirent, created by operations that add
fragments to configfs tree (mkdir and configfs_register_{subsystem,group}).
Will be used in the next commit to provide exclusion between fragment
removal and ->show/->store calls.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Christoph Hellwig <hch@lst.de>

diff --git a/fs/configfs/configfs_internal.h b/fs/configfs/configfs_internal.h
index f752d83..520f181 100644 (file)
--- a/fs/configfs/configfs_internal.h
+++ b/fs/configfs/configfs_internal.h
@@ -20,6 +20,15 @@
 #include <linux/list.h>
 #include <linux/spinlock.h>
 
+struct configfs_fragment {
+       atomic_t frag_count;
+       struct rw_semaphore frag_sem;
+       bool frag_dead;
+};
+
+void put_fragment(struct configfs_fragment *);
+struct configfs_fragment *get_fragment(struct configfs_fragment *);
+
 struct configfs_dirent {
        atomic_t                s_count;
        int                     s_dependent_count;
@@ -34,6 +43,7 @@ struct configfs_dirent {
 #ifdef CONFIG_LOCKDEP
        int                     s_depth;
 #endif
+       struct configfs_fragment *s_frag;
 };
 
 #define CONFIGFS_ROOT          0x0001
@@ -61,8 +71,8 @@ extern int configfs_create(struct dentry *, umode_t mode, void (*init)(struct in
 extern int configfs_create_file(struct config_item *, const struct configfs_attribute *);
 extern int configfs_create_bin_file(struct config_item *,
                                    const struct configfs_bin_attribute *);
-extern int configfs_make_dirent(struct configfs_dirent *,
-                               struct dentry *, void *, umode_t, int);
+extern int configfs_make_dirent(struct configfs_dirent *, struct dentry *,
+                               void *, umode_t, int, struct configfs_fragment *);
 extern int configfs_dirent_is_ready(struct configfs_dirent *);
 
 extern void configfs_hash_and_remove(struct dentry * dir, const char * name);
@@ -137,6 +147,7 @@ static inline void release_configfs_dirent(struct configfs_dirent * sd)
 {
        if (!(sd->s_type & CONFIGFS_ROOT)) {
                kfree(sd->s_iattr);
+               put_fragment(sd->s_frag);
                kmem_cache_free(configfs_dir_cachep, sd);
        }
 }

diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c
index 21a7956..1df65c2 100644 (file)
--- a/fs/configfs/dir.c
+++ b/fs/configfs/dir.c
@@ -151,11 +151,38 @@ configfs_adjust_dir_dirent_depth_after_populate(struct configfs_dirent *sd)
 
 #endif /* CONFIG_LOCKDEP */
 
+static struct configfs_fragment *new_fragment(void)
+{
+       struct configfs_fragment *p;
+
+       p = kmalloc(sizeof(struct configfs_fragment), GFP_KERNEL);
+       if (p) {
+               atomic_set(&p->frag_count, 1);
+               init_rwsem(&p->frag_sem);
+               p->frag_dead = false;
+       }
+       return p;
+}
+
+void put_fragment(struct configfs_fragment *frag)
+{
+       if (frag && atomic_dec_and_test(&frag->frag_count))
+               kfree(frag);
+}
+
+struct configfs_fragment *get_fragment(struct configfs_fragment *frag)
+{
+       if (likely(frag))
+               atomic_inc(&frag->frag_count);
+       return frag;
+}
+
 /*
  * Allocates a new configfs_dirent and links it to the parent configfs_dirent
  */
 static struct configfs_dirent *configfs_new_dirent(struct configfs_dirent *parent_sd,
-                                                  void *element, int type)
+                                                  void *element, int type,
+                                                  struct configfs_fragment *frag)
 {
        struct configfs_dirent * sd;
 
@@ -175,6 +202,7 @@ static struct configfs_dirent *configfs_new_dirent(struct configfs_dirent *paren
                kmem_cache_free(configfs_dir_cachep, sd);
                return ERR_PTR(-ENOENT);
        }
+       sd->s_frag = get_fragment(frag);
        list_add(&sd->s_sibling, &parent_sd->s_children);
        spin_unlock(&configfs_dirent_lock);
 
@@ -209,11 +237,11 @@ static int configfs_dirent_exists(struct configfs_dirent *parent_sd,
 
 int configfs_make_dirent(struct configfs_dirent * parent_sd,
                         struct dentry * dentry, void * element,
-                        umode_t mode, int type)
+                        umode_t mode, int type, struct configfs_fragment *frag)
 {
        struct configfs_dirent * sd;
 
-       sd = configfs_new_dirent(parent_sd, element, type);
+       sd = configfs_new_dirent(parent_sd, element, type, frag);
        if (IS_ERR(sd))
                return PTR_ERR(sd);
 
@@ -260,7 +288,8 @@ static void init_symlink(struct inode * inode)
  *     until it is validated by configfs_dir_set_ready()
  */
 
-static int configfs_create_dir(struct config_item *item, struct dentry *dentry)
+static int configfs_create_dir(struct config_item *item, struct dentry *dentry,
+                               struct configfs_fragment *frag)
 {
        int error;
        umode_t mode = S_IFDIR| S_IRWXU | S_IRUGO | S_IXUGO;
@@ -273,7 +302,8 @@ static int configfs_create_dir(struct config_item *item, struct dentry *dentry)
                return error;
 
        error = configfs_make_dirent(p->d_fsdata, dentry, item, mode,
-                                    CONFIGFS_DIR | CONFIGFS_USET_CREATING);
+                                    CONFIGFS_DIR | CONFIGFS_USET_CREATING,
+                                    frag);
        if (unlikely(error))
                return error;
 
@@ -338,9 +368,10 @@ int configfs_create_link(struct configfs_symlink *sl,
 {
        int err = 0;
        umode_t mode = S_IFLNK | S_IRWXUGO;
+       struct configfs_dirent *p = parent->d_fsdata;
 
-       err = configfs_make_dirent(parent->d_fsdata, dentry, sl, mode,
-                                  CONFIGFS_ITEM_LINK);
+       err = configfs_make_dirent(p, dentry, sl, mode,
+                                  CONFIGFS_ITEM_LINK, p->s_frag);
        if (!err) {
                err = configfs_create(dentry, mode, init_symlink);
                if (err) {
@@ -599,7 +630,8 @@ static int populate_attrs(struct config_item *item)
 
 static int configfs_attach_group(struct config_item *parent_item,
                                 struct config_item *item,
-                                struct dentry *dentry);
+                                struct dentry *dentry,
+                                struct configfs_fragment *frag);
 static void configfs_detach_group(struct config_item *item);
 
 static void detach_groups(struct config_group *group)
@@ -647,7 +679,8 @@ static void detach_groups(struct config_group *group)
  * try using vfs_mkdir.  Just a thought.
  */
 static int create_default_group(struct config_group *parent_group,
-                               struct config_group *group)
+                               struct config_group *group,
+                               struct configfs_fragment *frag)
 {
        int ret;
        struct configfs_dirent *sd;
@@ -663,7 +696,7 @@ static int create_default_group(struct config_group *parent_group,
                d_add(child, NULL);
 
                ret = configfs_attach_group(&parent_group->cg_item,
-                                           &group->cg_item, child);
+                                           &group->cg_item, child, frag);
                if (!ret) {
                        sd = child->d_fsdata;
                        sd->s_type |= CONFIGFS_USET_DEFAULT;
@@ -677,13 +710,14 @@ static int create_default_group(struct config_group *parent_group,
        return ret;
 }
 
-static int populate_groups(struct config_group *group)
+static int populate_groups(struct config_group *group,
+                          struct configfs_fragment *frag)
 {
        struct config_group *new_group;
        int ret = 0;
 
        list_for_each_entry(new_group, &group->default_groups, group_entry) {
-               ret = create_default_group(group, new_group);
+               ret = create_default_group(group, new_group, frag);
                if (ret) {
                        detach_groups(group);
                        break;
@@ -797,11 +831,12 @@ static void link_group(struct config_group *parent_group, struct config_group *g
  */
 static int configfs_attach_item(struct config_item *parent_item,
                                struct config_item *item,
-                               struct dentry *dentry)
+                               struct dentry *dentry,
+                               struct configfs_fragment *frag)
 {
        int ret;
 
-       ret = configfs_create_dir(item, dentry);
+       ret = configfs_create_dir(item, dentry, frag);
        if (!ret) {
                ret = populate_attrs(item);
                if (ret) {
@@ -831,12 +866,13 @@ static void configfs_detach_item(struct config_item *item)
 
 static int configfs_attach_group(struct config_item *parent_item,
                                 struct config_item *item,
-                                struct dentry *dentry)
+                                struct dentry *dentry,
+                                struct configfs_fragment *frag)
 {
        int ret;
        struct configfs_dirent *sd;
 
-       ret = configfs_attach_item(parent_item, item, dentry);
+       ret = configfs_attach_item(parent_item, item, dentry, frag);
        if (!ret) {
                sd = dentry->d_fsdata;
                sd->s_type |= CONFIGFS_USET_DIR;
@@ -852,7 +888,7 @@ static int configfs_attach_group(struct config_item *parent_item,
                 */
                inode_lock_nested(d_inode(dentry), I_MUTEX_CHILD);
                configfs_adjust_dir_dirent_depth_before_populate(sd);
-               ret = populate_groups(to_config_group(item));
+               ret = populate_groups(to_config_group(item), frag);
                if (ret) {
                        configfs_detach_item(item);
                        d_inode(dentry)->i_flags |= S_DEAD;
@@ -1247,6 +1283,7 @@ static int configfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode
        struct configfs_dirent *sd;
        const struct config_item_type *type;
        struct module *subsys_owner = NULL, *new_item_owner = NULL;
+       struct configfs_fragment *frag;
        char *name;
 
        sd = dentry->d_parent->d_fsdata;
@@ -1265,6 +1302,12 @@ static int configfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode
                goto out;
        }
 
+       frag = new_fragment();
+       if (!frag) {
+               ret = -ENOMEM;
+               goto out;
+       }
+
        /* Get a working ref for the duration of this function */
        parent_item = configfs_get_config_item(dentry->d_parent);
        type = parent_item->ci_type;
@@ -1367,9 +1410,9 @@ static int configfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode
        spin_unlock(&configfs_dirent_lock);
 
        if (group)
-               ret = configfs_attach_group(parent_item, item, dentry);
+               ret = configfs_attach_group(parent_item, item, dentry, frag);
        else
-               ret = configfs_attach_item(parent_item, item, dentry);
+               ret = configfs_attach_item(parent_item, item, dentry, frag);
 
        spin_lock(&configfs_dirent_lock);
        sd->s_type &= ~CONFIGFS_USET_IN_MKDIR;
@@ -1406,6 +1449,7 @@ out_put:
         * reference.
         */
        config_item_put(parent_item);
+       put_fragment(frag);
 
 out:
        return ret;
@@ -1574,7 +1618,7 @@ static int configfs_dir_open(struct inode *inode, struct file *file)
         */
        err = -ENOENT;
        if (configfs_dirent_is_ready(parent_sd)) {
-               file->private_data = configfs_new_dirent(parent_sd, NULL, 0);
+               file->private_data = configfs_new_dirent(parent_sd, NULL, 0, NULL);
                if (IS_ERR(file->private_data))
                        err = PTR_ERR(file->private_data);
                else
@@ -1732,8 +1776,13 @@ int configfs_register_group(struct config_group *parent_group,
 {
        struct configfs_subsystem *subsys = parent_group->cg_subsys;
        struct dentry *parent;
+       struct configfs_fragment *frag;
        int ret;
 
+       frag = new_fragment();
+       if (!frag)
+               return -ENOMEM;
+
        mutex_lock(&subsys->su_mutex);
        link_group(parent_group, group);
        mutex_unlock(&subsys->su_mutex);
@@ -1741,7 +1790,7 @@ int configfs_register_group(struct config_group *parent_group,
        parent = parent_group->cg_item.ci_dentry;
 
        inode_lock_nested(d_inode(parent), I_MUTEX_PARENT);
-       ret = create_default_group(parent_group, group);
+       ret = create_default_group(parent_group, group, frag);
        if (ret)
                goto err_out;
 
@@ -1749,12 +1798,14 @@ int configfs_register_group(struct config_group *parent_group,
        configfs_dir_set_ready(group->cg_item.ci_dentry->d_fsdata);
        spin_unlock(&configfs_dirent_lock);
        inode_unlock(d_inode(parent));
+       put_fragment(frag);
        return 0;
 err_out:
        inode_unlock(d_inode(parent));
        mutex_lock(&subsys->su_mutex);
        unlink_group(group);
        mutex_unlock(&subsys->su_mutex);
+       put_fragment(frag);
        return ret;
 }
 EXPORT_SYMBOL(configfs_register_group);
@@ -1842,10 +1893,17 @@ int configfs_register_subsystem(struct configfs_subsystem *subsys)
        struct dentry *dentry;
        struct dentry *root;
        struct configfs_dirent *sd;
+       struct configfs_fragment *frag;
+
+       frag = new_fragment();
+       if (!frag)
+               return -ENOMEM;
 
        root = configfs_pin_fs();
-       if (IS_ERR(root))
+       if (IS_ERR(root)) {
+               put_fragment(frag);
                return PTR_ERR(root);
+       }
 
        if (!group->cg_item.ci_name)
                group->cg_item.ci_name = group->cg_item.ci_namebuf;
@@ -1861,7 +1919,7 @@ int configfs_register_subsystem(struct configfs_subsystem *subsys)
                d_add(dentry, NULL);
 
                err = configfs_attach_group(sd->s_element, &group->cg_item,
-                                           dentry);
+                                           dentry, frag);
                if (err) {
                        BUG_ON(d_inode(dentry));
                        d_drop(dentry);
@@ -1879,6 +1937,7 @@ int configfs_register_subsystem(struct configfs_subsystem *subsys)
                unlink_group(group);
                configfs_release_fs();
        }
+       put_fragment(frag);
 
        return err;
 }

diff --git a/fs/configfs/file.c b/fs/configfs/file.c
index eee6281..9d5e888 100644 (file)
--- a/fs/configfs/file.c
+++ b/fs/configfs/file.c
@@ -488,7 +488,7 @@ int configfs_create_file(struct config_item * item, const struct configfs_attrib
 
        inode_lock_nested(d_inode(dir), I_MUTEX_NORMAL);
        error = configfs_make_dirent(parent_sd, NULL, (void *) attr, mode,
-                                    CONFIGFS_ITEM_ATTR);
+                                    CONFIGFS_ITEM_ATTR, parent_sd->s_frag);
        inode_unlock(d_inode(dir));
 
        return error;
@@ -510,7 +510,7 @@ int configfs_create_bin_file(struct config_item *item,
 
        inode_lock_nested(dir->d_inode, I_MUTEX_NORMAL);
        error = configfs_make_dirent(parent_sd, NULL, (void *) bin_attr, mode,
-                                    CONFIGFS_ITEM_BIN_ATTR);
+                                    CONFIGFS_ITEM_BIN_ATTR, parent_sd->s_frag);
        inode_unlock(dir->d_inode);
 
        return error;